My knees are bad but I figure I am too old to get too carried away about surgery. I get shots now and then and do exercises. Acqutainance of mine had knee surgery, died shortly after from complications. Another friend, old customer, wished he had never had his done. Another fought for a couple years and it finally worked out pretty well. Another is have the third replacement in same knee due to infection and other problems. Now, good friend has had both replaced and it worked out good but he cannot kneel down. So, mine will have to get a lot worse and I will probably die from something else first.

I cannot find any thing in parts book to verify this, BUT , my head is telling me that the very last 560's came with one piece clamp with key in clamp and no key way in the wheel. Reason to eliminate wheels cracking in the key area on wheel. I know I had a bunch of them off when working on them and pre delivery service when they were new but cannot prove it . I don't have service bulletins that old as I only go back to about 72 and then not a complete set.

I would unhook the plug connector and test the power with a test light rather than a volt meter. If you can light up a test light on each of the two power pins while hooking other end of test light to the ground pin I would say you have plenty of voltage, current etc to operate the data center. I have seen many inline fuse connectors (down by other fuse in separate wire)that make poor connections feeding that second power pin (I'm thinking it is pin 10 but not one hundred percent sure) and sometime the fuse holder of that top 5 amp fuse is a problem also. Power to fuse comes from cab relay so good connection necessary there also.
If any thing leaving the data center like senders was causing voltage to drop you would blow that fuse because something would be drawing too much. Also, to be honest with you, I don't know for absolute sure what voltage is fed to any of the senders as it could very well be knocked down coming out of data center. Most all computer senders operate on 5 volts but guess I never tested voltage to senders.
At any rate, if you have power enough to run a test light and going through the ground pin in connector, your unit should light up. Might go crazy, but light up.

I have no way of knowing anything that has been added by an owner. Hydro had red temp light but not by the other warning lamps in gauge instrument cluster. Red light for transmission oil pressure has to come on when depressing clutch on gear drive or something is not working. Like I said, a test of all lamps is provided with key switch and also the transmission oil pressure light should come on anything switch is on and engine not running.

Your original post indicates to me that you are trying to get the three bolts out that fasten the flat plate on the end of the hydraulic lines that go to the rear. You can get them up far enough to replace the two 0-rings without removing the valve if that is what you are after. Hard to get the bolts for sure. If you need to replace O-rings between valves or on the valve levers then, yes whole valve stack has to come loose and out.

There is only one light for transmission and that is the red light on the left hand end of the row of lights. It is the one that comes on when you depress the clutch. It is monitoring transmission lubrication pressure and is that sender on the MCV just like all 706 on up.
Like I said, red light is transmission oil pressure, next light to the right of first light is an amber light with a symbol that is supposed to represent brakes, then another amber light with an arrow pointing down through I think and represents dirty air cleaner, finally light on the right is for the coolant level. There is a probe in the top radiator tank that has to be submerged with coolant so it can seek ground and through a module on the back side of instrument panel it turns light on if coolant gets below the level of that probe. All that probe is just a solid steel rod and nothing to go bad except possibly poor connection or crud on the probe. Radiator has to be grounded and sometimes those rubber center bushing makes poor contact and so module cannot turn light off. Often times it is a good idea to run a wire from one of those mounts to a good ground.
You do realize that there is a test position to make sure all the warning lights are working. You turn ignition switch to start with out depressing clutch and having range transmission out of park so tractor will not try to start.
Also, no temperature indicators in those warning light as that is a separate gauge below warning lights and has a needle gauge.

The rod that pulls it out of park has no adjustment on it. That is the rod you have to make sure is all the way forward so the bellcrank is over center and touching the raised spot on cover. Other adjustments are to get lever into proper alignment with slots over in quadrant.
Just jackup a rearwheel and turn it(will turn hard due to wet brakes) by hand and you will hear park making noise if that is your problem .
Same engineer, different orders from head quarters.

If it worked ok before you split I would say it is due to the installation of the steering shaft. Make sure that the shaft going into the bolster can move back and forth on the splines in knuckle. When you turn one direction, the shaft has to move out and other direction shaft has to move in . If by chance the knuckle is pinned, welded or clamped to spline due to worn out splines(common methods for repairing worn out spline rather than replace shaft ) then the entire steering shaft has to move back and forth all the way to the steering wheel.

With the floor out, you can easily see if it is coming all the way out of park. The linkage pivot has to flip all the way over until it touches the raised stop. Like I said before, could be several different reasons so start with simple ones and eliminate those before any major tear down. Only making a noise while moving could well be not all the way out of park and a simple fix. If it makes a noise when in neutral and clutch engaged then forget the park .

If tractor is in two gears at the same time it will not move. The engine will labor and kill when engaging the clutch. As far as the nut, that is not a certain, just a good possibility. You would need to drain front section and remove lower plate to see if lower shaft has moved forward. If nut is off you will have a major repair of splitting between transmission and rear housing. That is why you have to do a bunch of checking to find out before doing a lot of unnecessary teardown. Could even be shift rail or fork. Can't tell much more from here. Others may have more ideas of what to look for.

You did not indicate if tractor still moved or not. Sounds like the nut on bottom shaft of speed transmission came off and all gears on lower shaft have moved ahead. And, Dad is right, no amount of oil is going to help you what ever the problem ends up being from your description.
Little more information would help .

That engine has a bypass type oil filter. In other words, only a small portion of the oil that is delivered from the oil pump is routed through the filter and directly back to the oil pan. That portion of the total oil flow from pump is regulated by a small hole in the bolt that the oil filter mounts to or in the oil filter. So, if the original bolt with that orfice in is intact, the oil filter will have no effect on oil pressure. You could totally block that flow through filter and it would not affect oil pressure. On the other hand, if that small orfice (hole) was not in place, or if the filter it's self has the controlling orfice rather than the mounting bolt, and the filter you used does not have that restricting orfice, it could be dumping a whole lot of oil right back to the pan.
Take a close look at your oil filter base, bolt, and filter to see where orfice is. If orfice is in place within filter or mounting bolt. filter is not your problem. I have no experience with the spin on filters on that model but have worked on many of those engines in several other applications and the orfice is always right in the long bolt holding filter canister in place. But, at any rate, there has to be a restricting orfice no matter what filter is used.
IH had a fool proof system and then someone had to reengineer it to a spin on filter where wrong application of filters can mess up the works.